This invention relates to the field of electronic door locks. More particularly, this invention relates to a multiple reader stand-alone door lock system for securing a door.
It is known in the field of electronic door locks to use a stand-alone electrically controlled lock to secure the door to a door frame. Such locks typically employ an access code system to permit selective operation of the electrically controlled lock. The access code system generally has a single code reader device for receiving an access code from a user of the door. The access code system can be a key pad or a card reader. The door lock stores valid user codes. Entry of a valid user access code at the reader unlocks the door lock to permit access.
Electrically controlled door locks have found acceptance in business and university settings. For example, a door lock system may secure a dormitory room. Each resident of the room is issued an individual valid access code for the particular lock that secures the room. For safety and maintenance reasons, it is also required that security and maintenance personnel be able to access the dormitory room. Therefore, each safety or maintenance person is also issued an individual access code for the door lock. Due to the large number of secured doors at a university, it is generally required that a single universal code be available to each safety or maintenance person to permit entry to large blocks of secured doors. If, however, the universal code is compromised, unauthorized personnel can gain entry to a large number of secured areas. Security problems are complicated by the multiple overlapping universal codes which allow access to blocks of overlapping secured areas.
It is generally preferred that security and maintenance personnel have a universal code unique to each individual. Therefore, for an individual door lock system, the individual system will unlock not only for residents of the dormitory room, but also the lock will unlock for a large number of additional universal codes. The greater the number of valid codes for a particular doorway, the greater the possibility that random entry of access codes will release the lock. When a universal code has been compromised, all the doors within a block or on the system must be individually reprogrammed to delete the old universal code and enter a new universal code.
When a universal code has been compromised, unauthorized personnel can readily enter large blocks of secured areas. To alleviate these and other deficiencies, door lock systems to which the invention relates have employed card readers, contact activatable readers or other electronic devices that cause the lock to release for access when a proper "key" is employed. The "key" may be a magnetic card, microchip contact device or other electromagnetic device. A deficiency of "key" systems is that in a university setting, students frequently lock themselves out of their rooms when they fail to carry the "key" or the "key" is misplaced, lost or stolen. Security personnel can spend a significant portion of time unlocking doors, electronically rekeying the lock system and replacing lost keys.